Stored procedures seem like a win but the big problem is that while I could write the rest of the software in a very nice modern language like Rust, or more practically in C# since my team all know C# if I write a stored procedure it will be in Transact-SQL because that's the only choice.

T-SQL was not a good programming language last century when it was vaguely current, and so no I do not want to write any significant amount of code in T-SQL. For my sins I maintain a piece of software with huge T-SQL procedures (multi-page elaborations by somebody who really, really like this stuff) and they're a nightmare. The tooling doesn't really believe in version control, the diagnostics when you make a mistake are either non-existent or C++ style useless spew.

We hire a lot of very junior developers. People who still need to be told not to comment out code in release, that variable numbers are for humans to read not machines, that sort of thing. We're not quite hiring physicists to write software (I have done that at a startup) but it's close. However, none of the poor "My first program" code I see in a merge request by a new hire is anywhere close to as unreadable as the T-SQL we already own and maintain.